In a typical petrol/diesel or so-called gasoline dispensing station with an underground fuel storage system, dispensing pumps are arranged on an island with the fuel storage tank(s) situated away from the island. A canopy is supported on a separate foundation poured on site, the island being supported on a similar but independent foundation. The tank(s) are sited on a slab or with “dead men”, polyester webbing bands or straps of wire rope to prevent uplift and rotation of the tank(s).
There are three main disadvantages of this arrangement. Firstly, multiple excavations and foundations have to be made for the tank(s), the island(s) and the canopy, all of which increases cost. Secondly, due to the distance between the tank(s) and the island(s) and therefore the pumps, the tank(s) need a deeper excavation to cater for pipe runs. In addition, this type of set up requires relatively long runs of pipe that may need joints along their length. This in turn increases the potential for ground contamination. Lastly, the site needs to be large enough to accommodate these various separate components.
Above ground fuel dispensing systems are also known and one such dispensing station is known from SE-B383707. In this case the foundation for the fuel station is arranged above ground. The fuel pumps and the frame structure for the canopy roof are mounted on top of this foundation. This arrangement with the above ground tank and the fuel pumps in front of it presents some problems. Firstly, due to the size of the foundation the fuel pumps can only be attended by the customers from one side. Secondly, there are security aspects to be taken into consideration. There is always the risk of explosion in the event that a vehicle or the like crashes into the fuel station. Furthermore, it is relatively easy for unauthorised personnel to gain access to the above ground fuel tank(s). Thirdly, seasonal temperature fluctuations must be considered because the expansion of fuel in the tank differs significantly with the temperature.
Attempts have been made to address some of these problems. For example, EP 0686105B1 (U-Cont Limited) describes an integral unit for the construction of a petrol filling station. It describes a tank, pump island and rain shelter pre-fabricated onto one, common foundation prior to location on the construction site. Built into the construction is a frame structure for the canopy roofing which is adapted to be supported directly on the foundation and thus the bearing loads are directed past and away from the fuel tank(s). As a result, the natural buoyancy of the tank(s) still presents problems in areas where there is a high water table or areas which are prone to flooding. The tank must therefore still be strapped down as in the previously described prior art. There are further disadvantages of this design. The storage tank sits inside a load-bearing framework. This means that if the tank develops a leak or has to be replaced for any reason the entire structure, including the foundations, has to be removed. In addition, the extent of the excavation needed to accommodate this type of construction is significantly larger than that required to accommodate a conventional tank alone.
U.S. Pat. No. 5,526,964 (Petro-First Inc) also describes a pre-fabricated modular fuel dispensing system. In this case the system includes a foundation module with an underground fuel reservoir to store fuel to be dispensed and a conduit containment trough to house fuel supply conduits and a fuel dispensing conduit. This fuel dispensing module includes a pump island which supports fuel dispensing devices and also supports a canopy roof and its supporting columns. The foundation module, fuel dispensing module and canopy module are configured to be integrated into a unitised, mutually supportive structure. However, the canopy supports can only be located at either end of the fuel reservoir in this design. In many circumstances, this is too restrictive to be practical, particularly in larger filling stations which require an extensive canopy roof.
It is an object of the present invention to overcome or at least mitigate some or all of the problems outlined above.